In recent years, both the amount of required communications as well as the requirements on communications increased significantly. In particular, mobile communications systems such as Global System for Mobile Communication (GSM) and packet data networks such as the Internet are concerned with this development. As an example, packet-switched mobile communication systems such as Code Division Multiple Access (CDMA) networks have been introduced.
It is to be noted that many of the aspects discussed in the following relating to CDMA networks are only intended to be illustrative and exemplary for all kinds of comparable Third Generation (3G) networks, e.g. Universal Mobile Telecommunications System (UMTS) or General Packet Radio Service (GPRS).
An IP Multimedia Subsystem (IMS) provides for handling multimedia applications (e.g. still and moving images).
After an establishment of a session between e.g. a user equipment and a network element, a policy often has to be defined for the established communication session. A session can be understood as a logical/virtual connection and is to be established in the beginning of user activity. Such policy specifies communication requirements related to the respective session, e.g. the required quality of service (QoS) for the data packets to be transmitted, or required security aspects. Usually, specialized functions and/or network elements are provided for policy-related purposes.
Errors occurring during policy control are usually handled by network elements. For this purpose, predetermined error codes may be used in order to identify the type of error and to choose a procedure for handling it.